1. Field of the Invention
This invention relates to improvements in doors, and more particularly, to improvements in corner joints, panel mounting, and center panel board mountings of doors.
2. Description of the Prior Art
In the manufacture of doors, particularly of doors of relatively heavy materials, such as of solid wood construction, one of the design problems most frequently encountered is in providing means for counteracting the forces of the weight of the door upon the elements forming the door. For example, typically in a door having a pair of parallel rails connected at their ends by a pair of parallel stiles, when the door is hung upon one of the stiles, for example, the weight of the other stile and of the rails presents a moment at the interconnection between the hinged stile and the top and bottom rails tending to allow the rails to rotate downwardly and away from the hinged stile. Likewise, the non-hinged stile will tend to separate from the rails by virtue of similar moments acting at their joints.
In attempts to overcome this separation tendency, one or more, and typically three, pins or rods are located at the rail-stile junction, partially extending into the rail and partially extending into the stile. Although the pins have been successful to some extent in lighter doors, in heavier doors, they lend insufficient strength to the door to withstand the weight which the elements of the door present.
In the manufacture of doors, one of the designs which has been found to be particularly attractive and of widespread favor is that in which the center panel, i.e., the panel inserted within the rectangular area defined by the rails and stiles, is of a plurality of parallel boards. The boards are mounted edge to edge, and fastened at the outer edges thereof to the rails and stiles. In this door design, the weight of the solid boards of the center panel compound the weight problem above mentioned. Additionally, numerous other problems are presented by the multiple board panel, for example, the mounting of the panel to the rails and stiles presents a significant problem in that an airtight interface between the boards of the panel and the rails or stiles to which they are adjacently mounted, although necessary, is difficult to achieve. If the boards are merely nailed and/or glued in place, the shrinkage or expansion of one or more of the boards may destroy the airtight seal, if not the entire center panel door frame connection. Additionally, the airtight requirement of the door is difficult to achieve because of the interconnections between adjacent boards making up the center panel. Thus, for example, if a common tongue and groove connection is made between adjacent boards, the shrinkage of one board to an extent approximately equal to the width of the tongue would destroy the airtight seal between the adjacent boards.
Typical tongue and groove connections, known in the art, are generally such that a single groove is provided centrally along the length of one of the boards to be connected. A mating tongue is presented running along the length of the other board to be mounted. The two boards are interconnected by mating the tongue and groove of the respective boards and subsequently affixing the boards in the mating position by glue, nails or other such fastening means.
However, another problem encountered in the mounting of the number of boards edge to edge is the warping which can take place by one or more of the boards. Ordinarily, if the door is exposed to different environmental conditions on either side, for example, temperature, humidity, and so forth, the boards of the door naturally tend to warp in one direction or the other, depending on the orientation of the grain of the boards. This problem is compounded in the mounting of one board upon another by the common tongue and groove method, as described above. For example, the orientation of one board upon another is dependent principally upon the manner in which the tongue and groove of the boards if formed. Once the tongue and groove are formed in any particular board, its orientation in the final panel is fixed. It cannot be turned in either direction, as would be desirable. Thus, the resulting center panel may include adjacent boards having haphazardly oriented grain patterns, which are randomly oriented depending upon the manner in which the tongue and grooves are formed in the individual boards.